Retractable hydrostabilizer for airplanes



April 4, 1939- R. J. MINSHALL :TAL

RETRACTABLE HYDROSTABILIZER FOR AIRPLANES Filed Aug. a, 1957 4 Sheets-Sheet 1 ZSnoentow Robert J Minshall u -W6HS {M (Ittomeg April 4, 1939. R. J. MINSHALL ET AL 2,153,265

-RETRACTABLE HYDROSTABILIZER FOR AIRPLANES Filed Aug. 3, 1937 4 Sheets-Sheet 2 ell s attorney April 4, 1939. R. J. MINSHALL ET AL 2,153,266

RETRACTABLE HYDROSTABILIZER FOR AIRPLANES Filed Aug. 3, 1957 4 Sheets-Sheet 3 3nventor s Robert J-'Minsholll By Edward C -We11s (Ittorneg April 4, 1939.

R. J. MINSHALL Er AL RETRACTABLE HYDROSTABILIZER FOR AIRPLANES 4 Sheets-Sheet 4 Filed Aug. 5, 1937 Jnventors Robert J Minshall Edward C.Wel1s I Gttomeg v Patented Apr. 4, 1939 UNITED STATESPATENT} OFFICE RETRACTABLE HYDROSTABILIZER FOR AIRPLANES Robert J. Minshall and Edward 0. wens, Seattle, Wash., assignors to Boeing Aircraft Company, Seattle, Wash., a corporation of Washington Application August 3, 1937-, Serial No. 157,122 5 Claims. (01. 244-102 'I'his'invention, in its primaryaspect, pertains to airplanes of a type which are intended, to float upon water, though in another aspect it pertains to any craftoperable as' a high-speed surface 5 craft. While the aims of the invention may be realized with all types of airplanes intended to land upon and take ofi from water, whether fly ing boats or pontoon-supported,'it will generally be employed with flying boats, inasmuch as ponm toon-supported airplanes are normally small and have floats so placed as to insure lateral stability while floating, especially in protected waters where they are chiefly used.

It is typical of airplanes intended to alight .15 upon water that means are provided to stabilize the airplane laterally, so that it will not roll and so that its wings will not dip into the water. In small planes this can often be sufficiently accomplished byv spreading two floats 20 apart, these constituting the sole displacement.

means to support the airplane upon the water, and constituting also the planing surfaces by which it may rise upon the surface and eventually take of! from the water.

25 In larger airplanes, however, it is necessary to .30 rigidly supported in position, and therefore a source of drag when the airplane is in flight, and when the float is no longer of any immediate value. Such floats have been made retractable by swinging them outwardly and upwardly into 35 alignment with the wings, to constitute the tips of the wings, or inwardly and upwardly to a positionwherein they are partly housed within and partly protrude from the under side of the wing, but in either such position, because of their necessary form for floating upon and taking oil from the water, they are not aerodynamically eificient, and produce an undueamount of drag. In addition, they reduce the maneuverability .of the airplaneon the water, since the airplane can not bebanked to make a turn at any speed, for if the floats, of small displacement, are to act as effective stabilizers when the airplane is operating as a displacement craft, they are so far outboard that they are in the way, and prevent banking while traveling on the surface.

Some designers prefer to employ sponsons, projecting laterally from the hull of a flying boat at the water line, these sponsons constituting the lateral stabilizing meanswhen the airplane floats,

but all such sponsons, so far as we are aware,

have been formed as an integral part of and fixed rigidly in a single position only to the hull of the flying boat, and permanently project'from such hull, and since they have little or no lift characteristics while in flight, but produce appreciable 5 drag, their presence, though necessary while floating, is undesirable when the airplane is in flight. Such sponsons, being closer to the center of buoyancy than wing-supported floats, permit somewhat greater surface maneuverability. However, they must act as displacement members while the airplane is floating, and asvanes when the airplane is acting as a hydroplane, or is on the step, and these somewhat different considerations rather closely limit their! location, shape, and position relative to the hull. As a result, it has heretofore been considered necessary to support and brace them as rigidly as possible from the aircraft structure, and such a rigid support and invariable position is not conducive to the absorption of shocks when landing, or to maneuverability at high speeds on the surface, when it is necessary to bank the airplane to any appreciable degree. The same considerations apply to a strictly surface craft acting at times as a hydroplane.

Accordingly it is a principal object of the present invention to provide hydrostabilizing means which are effective as to form and location when the airplane is acting either as a displacement craft or as a hydroplane, which facilitate maneuvering while. traveling on the surface, but which in flight can be retracted into a position of lower drag, thereby producing the greatest hull, or at both places, a further object is attained, namely, the structure as a whole may be made lighter by the omission of consideration of landing shocks and their transmission to structural members, in the design of the aircraft. By

the adjustment of angles the sponsons become maneuvering vanes, for better control of the craft while operating as a hydroplane, yet, being retractable, these maneuvering vanes may be moved to a position of lower drag, in flight, when they are no longer needed to facilitate maneuvering.

. longitudinal plane. Figure 1a is a detail of a It is a further object to arrange such hydrostabilizing means as-to form and location, and with relation to the hull and wings of a flying boat, that when retracted the hydrostabilizing means, and in some instances the strut or struts supporting or bracing them from the aircraft structure, will fill recesses provided in the hull and other parts of the aircraft structure, and will restore the surfaces thereof to full aerodynamic emcien'cy, thereby almost or completely eliminating drag due to the presence of the hydrostabilizing means or their adjuncts.

More specifically, it is an object to provide hydrostabilizing means of the general character indicated which may take the form of sponsons projecting laterally from the flying boat hull at or near the water line, and which will in general be retractable into recesses within the hull. It may be noted here that the term water line is used in a general sense. While the airplane is acting as a hydorplane the sponsons act as vanes upon the surface of the water, although one or the other may at times be lifted clear of the water. While the airplane is acting as a displacement craft, the sponsons will normally be partly submerged, serving as additional displacement members, or may on occasions be substantially wholly submerged. In stating that they are located at the water line it is meant that they are located in such a manner as to best fulfill these two normal functions.

It is a further object to provide such retractable hydrostabilizing means which will be retractable inwardly or toward the center of gravity of the airplane rather than outwardly. It is advantageous, in landing or taxiing, to concentrate the weight, so far as possible, adjacent the center of gravity, and to lessen the load necessary to be carried by wing spars and the like. This also makes the airplane more easily maneuverable in flight and while hydroplaning. By locating the hydrostabilizing means adjacent the hull there is avoided the necessity of strengthening wing spars to support and effect the operation of retractable wing tip floats.

It is a further object to provide such retractable hydrostabilizing means which can be made in a variety of forms to suit the ideas of different designers, which will occupy a minimum of space, and require the minimum of interference with structural, control, or load-carrying parts of the airplane, and which may be operated in a simple manner.

With these and other objects in mind, as will appear hereafter, our invention comprises the novel combination of an aircraft and such retractable hydrostabilizing means, and the relative formation and arrangement of the parts thereof, and of their retracting means, all as shown in the accompanying drawings, and as will be described in this specification and more particularly defined by the claims which terminate the same, v

In the accompanying drawings we have illustrated our invention embodied in various typical forms, the illustrations being diagrammatic in character.

Figure 1 is a front elevation of the center section of such an airplane, illustrating the hydrostabilizing means in its extended and in its retractedv positions, in a form and arrangement which is at present preferred by us, and Figure 2 isjin general a section therethrough on a vertical shock absorbing support for the hydrostabilizer at the hull.

Figure 3 is a section similar to Figure 2, but showing the entire hull of the flying boat, and illustrating a modified arrangement, and Figures 4 and 5 are views similar to Figure ,1, showing modifications, either of which corresponds to the arrangement of Figure 3.

Figures 6, 7, 8, 9,10, 11, 12 and 13 are all views similar to Figure 1, each showing a different modification.

While, as indicated above, the principles of this invention are applicable to any aircraft adapted or formed to float upon water, and indeed, in part to hydroplanes operating only upon the surface, it is principally applicable 'to flying boats, and will be described in conjunction with that type of airplane. Thus the hull I of the flying boat, provided in this instance with a V-bottom I0, is sustained in the air by wings ll projecting laterally from the upper part of or above the hull, and by motors driving propellers l2.'

The wing thus projectslaterally above the water line to a considerable distance at eachside of the hull, and being subject to the action of winds, Waves and other factors, tends to tilt the airplane laterally about the center of buoyancy, which is located within the hull. Such wings are usually constructed with spaced spars l3, acting as beams to sustain the load in flight, and it is desirable that these spars be not interrupted, as this requires added strengthening and consequent added weight, and itialso follows that they should be as light as possible.

The hydrostabilizer' 2, in the form shown in Figures 1 and 2, takes the form of a one-piece sponson projecting laterally from the hull at a level where it will be most effective for maintaining lateral stability, or for facilitating maneuverability, while the airplane is acting as a displacement craft or as ahydroplane, as pointed out above. The sponsons, when projected, are always at or near the water line. Their internal construction is largely immaterial, and to a con- .siderable degree their external form may be varied widely, and the present invention is not primarily concerned with either their internal structure or their external form. It is sufficient to note that the bottom of such a sponson, intended to act as a plane when hydroplaning upon the surface of the water, is not of a form which produces any appreciable aerodynamic lift in flight, nor is its upper surface usually formed to produce any appreciable lift, so that the sponson or hydrostabilizer, together with any strut means 3 bywhich it is braced from the airplane structure, in flight have usually constituted heretofore practically a dead drag.

In the form shown in Figures 1 and 2 the bottom of the hydrostabilizer 2 is provided with a step 20, although such a step is omitted in the form shown in Figure 3. Such a step may or may not be employed as proper design may indicate. Similarly the hydrostabilizer 2, as shown in Figure 1, is provided with a bulbous portion 2| at its outboard end, this constituting an added displacement correcting any tendency to dip the wing in this direction, since this buoyant portion 2| is thereby forced beneath the surface of the water, and by its displacement reacts, tending to force this side of the airplane upward. Such an enlargement may or may not be employed, and is not employed in the forms illustrated in other views, as for example in Figure 12.

Similarly the form andarrangement of the strut means 3 is immaterialin so far as the present invention is concerned, except as hereinafter pointed out, and indeed, strut means may be entirely omitted if its point of connection to the hull can be made sufficiently resistant to the hinge moments acting thereon. It is preferable that these strut means engage the hydrostabilizer at two points, spaced longitudinally of the aircraft, andithat they be similarly braced from the aircraft structure at two longitudinally spaced points, but this is largely a matter of design, and

I in no wise is to be considered as essential, through so shown in Figure 2. Likewise the point of connection of the strut or bracing means, both to the hydrostabilizer ,2 and to the aircraft structure, is important only as bearing on considerations which will appear hereafter, and the strut means is in some of the forms herein disclosed connected to the wing ll, outboard of its junc-v tion with the hull, and is in some instances connected directly withinthe hull.

The hydrostabilizer 2 as shown in Figures 1 and 2, in a form which at-present we prefer, is of a length, in a direction laterally of the aircraft, to afford proper stability, andyet to be housed entirely within the confines of the hull I, with the possible exception of the bulbous extremity 2|, if the latter be employed. Its operative or projected position is shown infull lines at the right of Figure I, and in dash lines it is shown in its retracted position. At the left of Figure 1 it is shown in full lines in its retracted position, with only the bulbous extremity 2| projecting from the outline of the hull. To accomplish this movement of the sponson from one position to another its inner end is pivotally connected at 42 to a nut 40 threaded upon a screw 4 joumaled within the hull, and appropriate means (not shown) are provided for accomplishing rotation of the screw 4 and consequent 'travel of the nut 40 lengthwise of the screw. The screw is set in a generally upright position, and the hull is recessed, as indicated at H, to receive the hydrostabilizer. The strut means 3lare pivotally connected at 32 to the stabilizer, outwardly of and parallel to the pivot 42, and at 3| to the wing, likewise upon a pivot axis parallel to the pivots 32 and 42, and outwardly of the junction of the wing with the hull a distance which is equal to the length or height of the strut means, so that in the retracted-position the pivot 32 .lies substantially at the junction of the wing with the hull, and the wing may be recessed in its under surface to receive the strut means. Preferably the strut means are disposed entirely between the spars 3, so that the latter are not interrupted. The reception of the strut means within the recesses in the under side of the wing v will close these recesses and will substantially restore the aerodynamic contour of the wing in flight. Likewise the upper surfaces of the sponson, at least such'portion thereof as lies beneath the wing in the retracted position, may be formed to come substantially flush with the surfaces of the hull, when in retracted position, and

in that way to restore the aerodynamic surfaces of the hull, thereby eliminating to the greatest degree possible any drag by reason of interruption of these surface sot the hull and of the wing.

It will be obvious that as the screw 4 is rotated the nut, traveling upward along the screw will draw the inboard 'endof the hydrostabilizer 2 upwardly and somewhat inwardly, the hydrostabilizer and the strut means 3 pivoting about the respective longitudinal pivots 32 and 3|, and

the hydrostabilizer about the parallel pivot 42. When the nut 40 reaches the upper end of. its limit of travel the hydrostabilizer will have been withdrawn into the hull within the recess l4 provided therefore, the strut means 3 will have been drawn inwardly and upwardly into its corresponding recess in the under side of. the wing, and the aerodynamic surfaces of both the hull and wing will have been substantially restored to continuity, and substantially all drag by reason of the hydrostabilizer and its strut means will have been eliminated. The bulbous extremity 2| may be left projecting from the hull at the chine thereof, but this produces no material drag, particularly as compared with the drag which would be produced by the hydrostabilizer were it left in its projected position. Moreover, because of this drag, previous hydrostabilizers, have been reduced as much as is safely possible in lateral extent, whereas with the present arrangement the hydrostabilizer may be extended laterally to a considerably greater degree, provided only that the height of the hull is sufficient to permit its retraction within the hull, which is readily possible with the large multiple-deck flying boats now constructedand projected.

' against rotation.

We prefer to include shock absorbing means between the outboard end of the hydrostabilizer and the aircraft structure to which the latter is braced. Such shock absorbing means are illustrated at 9, within the sponson 2, supporting the pivot 32 yieldably from the sponson. They might be arranged as a part of the strut means themselves, and are so shown in other forms. They may be capable of being lengthened or shortened to effect corresponding movement of the sponson, by hydraulic or other means, and shock absorbers capable of such operation are already known, hence we do not show means to accomplish such controlled lengthening or shortening. Such adjustment of the angle of the sponson, relative to the hull, .may be employed to facilitate banking of the airplane when running at high speed upon the surface.

Shock absorbing means may be employed between the pivot 42 and the aircraft structure, either in lieu of or in addition to the shock absorberv at 9. Thus, in Figure 1a, the nut 40 is shown connected to one of the relatively movable members, as the plunger SI, of a shock absorber, the cylinder 92 whereof supports the pivot mounting 42.

By effecting movement of one or both of the pivots 42 and 32 up or down, by controlled operation of the respective plungers through means known in the shock absorber art, the angle of the sponsons' relative to the hull may be controlled at will.

Itwill be observed that by the arrangement described a minimum of space is occupied within the hull by the hydrostabilizer recess or well, and that there is ample room for free access between the parts forward of such recess and aft thereof. Further, but little space or interruption of parts is required within the wing, and this is important inasmuch as the space within the wing, between the hull and the wing-mounted engines, is usually' engine controls, and conduits of various sorts, and as well as aileron and flap operating means and the like, and it is therefore important that a minimum of the space Within the wing be occupied by the devices which brace or operate the hydrostabilizer.

While but a single operating screw 4 has been shown in Figures 1 and 2, it is obvious that two or a greater number of such screws may be em-' ployed as the occasion demands.

The arrangement shown in Figure 3, which corresponds generally to the two slightly different forms shown in Figures 4 and 5, differs but slightly from the arrangement heretofore described. The operating screw or screws 4 are slightly more upright, and the strut means, designated 30, is preferably connected adjacent the outboard tip of the hydrostabilizer, or to the bulbous extremity 2|, as shown in Figure 4. Primarily the difference between this form of Figure 4 and that of Figures 1 and 2 is that the upper pivot 3| of the strut means is connected to a nut 50 which travels along a screw 5 disposed lengthwise of the wing, and which is synchronized, by any suitable means, not shown, with the operation of the retracting screw 4. During retraction the nut 50 is moved inwardly until in the retracted position the strut means lies substantially flush with the skin of the hull I, The strut means in addition may be covered with a fairing or skin, so

shaped as to cooperate with the skin of the hull to merge with the latter, and thus to close the recess l4 and to restore the streamline of the hull. In the arrangement shown in Figure 4 the bulbous extremity 2I is immovable with respect to the hydrostabilizer 2, and is withdrawn com--' pletely within the outline of the hull. In Figure '5, however, the bulbous extremity 22 is pivoted at 23 to the outer tip of the hydrostabilizer 2, and the strut means 30 is rigid with the bulbous extremity 22, the pivot at 23 being substituted for the pivot at 32. Thus during retraction the bulb- 011s extremity pivots somewhat about the pivot 23 with respect to the hydrostabilizer 2, and in the retracted position may be left projecting slightly from the outline of the hull, as shown in dash lines in Figure 5. In other respects this form is similar to that described with relation to Figure 4.

In Figure 6 the arrangement is similar to those previously described, although there is shown no bulbous extremity of the hydrostabilizer, but in this arrangement the strut means is formed as a member which is extensible or contractible in length, consisting, for example, of a cylinder or cylinders 93 within each of which is received a plunger94 of a shock absorber, pivotally mounted, in this instance at 3|, upon the hull itself, rather than from the wing I I. The portion 93 is pivoted at 32', as before, to the hydrostabilizer 2 outboard of the latters connection at 42 to the strut 40. Reciprocation of the plunger 94 within the cylinder 93, for retraction'of the sponson, is accomplished by suitable means, not illustrated, since the particular form and arrangement of these means is not in itself a part of our invention- The element 93, constituting part of the strut means, may be covered with a cover or fairing 95,

' and in the retracted position this fairing serves to close therecess in the hull which receives the hydrostabilizer 2.

hydrostabilizer.

wardly toward the wing tip. In effect this hydrostabilizer 24 ispivotally mounted at I5 upon the wing, the pivot axis l5 being longitudinally disposed, and the depending portion 35 from the pivot I5 downwardly to the hydrostabilizer constituting in effect a part of the strut means bracing the hydrostabilizer. Additional strut means are provided in this form, consisting of toggle links 36 pivotally connected at the lower end to the hydrostabilizer, and pivotally mounted in the aircraft structure at 3|. One of these links may be formed as ashock strut 9. By applying a force, as indicated by the arrow A, the toggle links 36 are broken and their extremities are caused to approach, thereby drawing upward the inboard end of the hydrostabilizer 24 until it is received within a recess provided in the hull I, the strut member 35 being likewise received in a recess in the under side of the wing. The surfaces of the hydrostabilizer 24 and the strut means 35 which will be exposed when in the retracted position, may be formed to reconstitute the angle at the junction between the wing and the hull, and to restore the streamline surfaces of the two.

In the arrangement shown in Figure 8 the hydrostabilizer 25, which is shown as provided with a bulbous extremity, is pivoted fixedly or through a suitable shock mount, at I6 to the hull adjacent the water line, and its outboard end is braced from the hull by toggle links 36'. By applying a force to the latter, as indicated by the arrow B, the outboard end of the hydrostabilizer is swung directly upwardly within its recess in the side of the hull, its under surface in this instance being formed to approximately restore the streamline surface of the side of the hull.

In the arrangement shown in Figure 9 the hydrostabilizer 2 is again pivoted at I6 to the hull, and is braced from the aircraft structure by cooperating extensible screw elements 33 and 34, or through an extensible shock absorber, previously described. In this instance it is provided with a bulbous extremity 22', pivoted at 23 to the outboard end of the sponson 2, and the movement of this member 22' is controlled by a link element 6, pivoted to the member 22 and within the hull in such manner that the member22 is maintained substantially upright during retraction, and in the fully retracted position is received within a recess provided for it in the under side of the wing II, as shown in dash lines in Figure 9 The arrangement shown in Figure 10 is similar to that shown in Figure 9, except that the pivot 23, which takes the place of the pivot 23, is disposed inboard from the extremity 22, thus dividing the hydrostabilizer into two relatively movable parts 2 and 26. This permits the hydrostabilizer as a whole to be made of somewhat greater lateral extent, and the bulbous extremity 22 may be received within a recess provided in an engine nacelle I2. Here the strut means 31, which may be of any type heretofore described, extends between the wing I I and the outer portion 26 of the Also the retracting means is shown in this instance as a screw 44 which is secured to the hydrostabilizer 2 outboard of its pivot I6, and a nut 45, which is journaled within the hull I, and which is rotated by a nut 46 engaged by a worm pinion 41, operated in turn through skew gears 48, whereby both of the hydrostabilizers may be retracted and projected conjointly through a drive gear 49 connected'to a suitable source of power and connected to both of the sets of skew gears 48. This, or any equivalent means, may be employed in any modification, to efiect simultaneous operation of the two hydrostabilizers.

In the arrangement shown in Figure 11 the hydrostabilizer is again formed of two separate parts 2 and 26, connected along a longitudinal pivot axis at 23', the inboard end of the hydrostabilizer being pivoted at It within the hull l. The strut means 38 is identical in principle to that described in conjunction with Figures 1 and 2, being pivoted at a fixed point 3| to the upper part of the aircraft structure and at 32' to the outboard end of the hydrostabilizer. A force applied in the direction of the arrow C will swing inwardly the inboard portion 2 of the hydrostabilizer, and the two portions 2 and 26 will break about the pivot 23' to assume finally the dash line position. 'In this latter retracted position the strut means 38 will lie substantially flush with the side of the hull and will close the recess therein provided for the reception of the hydrostabilizer.

Figure 12 illustrates an arrangement similar to that of Figure 7, the principal difference being in the manner of retraction, and in the provision of a continuation of the bottom surface of the hydrostabilizer from its outboard extremity inwardly to the hull I. This continuation consists of the member 21 pivoted at 28 to the inboard end of the hydrostabilizer 24, and the inboard end of this inward extension 21 is guided at 1 for movement along a track 10. Such upward movement'of the point I swings the hydrostabilizer 24 inwardly about the pivot l5 until it fills the junction between the wing II and the hull I, and in the final retracted position disposes the inward extension 21 in the dash line position above the strut element 35.

The arrangement shown in Figure 13 is similar to that shown in Figures 4 and 5. The inboard end of the hydrostabilizer 2' is pivotally connected to a nut 40 to travel along the upright screw 4, and its outboard end is braced from the aircraft structure by strut means 39, pivotally conrectly inwardly, the carriage 8 traveling along the track 80 until in the final retracted position the strut 39 or fairing carried thereby closes the, recess into which the hydrostabilizer has been retracted, restoring the streamline surfaces of the side of the hull.

What we claim as our invention is:

1. In combination with an airplane having a recessed hull formed to float upon the water, and having a wing projecting from the hull, above the water, a hydrostabilizer projecting laterally Irom the \hull adjacent the water line, strut meanssecured at its upper end to the wing upon a longitudinal pivotal axis, and pivotally secured at its lower end to the hydrostabilizer, and means to move the inboard end of the hydrostabilizer upward, thereby to swing the hydrostabilizer into an upright position within the hull recess, the several parts being so proportioned and organized as to swing the strut means, by such movement of the hydrostabilizer, into substantial coincidence with the wing.

2. In combination with a flying boat, the hull whereof is recessed beneath the wing, and the wing whereof is recessed from its junction with the hull outwardly, a hydrostabilizer projecting laterally from the hull, adjacent the water line, strut means pivotally connected at its lower end to the hydrostabilizer, and pivotallyfixedly connected to the under side of the wing at a distance from the hull substantially equal to the length of the strut means, and means to move the inboard end of the hydrostabilizer upwardly, thereby to move the hydrostabilizer into the hull recess, and to move the strut meansinto the wing recess.

3. In combination with a flying boat having a wing extending laterally above the water. a hydrostabilizer projecting laterally from the hull, adjacent the water line, an upright screw and a nut, one mounted in the hull and the other carried by the inboard end of the hydrostabilizer, whereby by rotation of the one to draw the inboard end of the hydrostabilizer upwardly, means bracing the outboard end of the hydrostabilizer from the wing thereabove, and means to swing the lower end of the bracing means inwardly, during upward movement of the inboard end of the hydrostabilizer, into a retracted position wherein the bracing means underlies the wing.

4. The combination of claim 3, wherein the hull is formed with a recess to receive the hydrostabilizer, and the wing is formed with a recess for the bracing means, the hydrostabilizer and bracing means in retracted position, substantially restoring the continuity of the skin of the hull and wing interrupted by such recesses. r

5. In combination with an airplane having a flotation hull and a wing projecting laterally therefrom above the water line, a hydrostabilizer projecting laterally from the hull at the water line, means to anchor its inboard end to the hull, a strut pivotally connected to and depending from the wing to the hydrostabilizer, and pivotally connected to the hydrostabilizer between the ends of the latter, means guiding the anchoring means for the inboard end of the hydrostabilizer for movement upwardly as parts move towards retracted position, the hull having a recess in its side, and the wing structure being pierced in continuation of such recess, means to retract the hydrostabilizer into such recess, with its inboard end penetrating the wing, the strut and said guide means cooperating to guide the outboard end of thehydrostabilizer into a retracted position at the lower end or the recess, and the strut points of connection to the wing and to the hydrostabilizer being so located, and the parts so organized, as to bring the strut, when parts are retracted, into substantial coincidence with the lower surface 01' the wing.

ROBERT J. MINSHALL.

EDWARD C. W'ELIB. 

